DESCRIPTION: This work is aimed at developing modern techniques of electron spin resonance (ESR) as general analytical tools for a wide range of biomedical studies and establishing a national biomedical ESR resource center involving collaborative biomedical research. This work will build upon the pioneering efforts in the laboratory of Freed in four-specific areas that show great promise for bringing ESR spectroscopy to it fullest potential: (1) Very high frequency (far-infrared [FIR]) ESR will be developed for application to biological material including spin-labelled proteins, lipids, and metalloproteins. This effort will be directed to improve the sensitivity of ESR to magnetic parameters, molecular structure, and molecular motion and to use a multifrequency approach to extract the complex dynamics of proteins and DNA. (2) The technique of two-dimensional Fourier-transform ESR (2D-FT-ESR) will be improved in sensitivity and resolution as required for biological systems. It will be developed for structural studies in biological materials based upon the nuclear modulation patterns with sharply increased resolution over conventional 1D methods. It will be extended to the study of spin-spin distances in multiply labeled biopolymers. 2D-FT-ESR will be developed to enhance the sensitivity of ESR to the complex motions of biomolecules. This will also provide a new means of measurement of rates of exchange between different environments in biological materials. (3) Fourier-transform (FT)-ESR Imaging techniques will be developed for the measurement of macroscopic lateral diffusion in biological systems and for investigating microscopic dynamics in biological transport phenomena. These efforts will significantly improve upon previous cw-ESR imaging methods and will include the extension to 2D-FT-ESR imaging. (4) Advanced algorithms for ESR spectral calculation will be developed for application to the new 2D-FT-ESR and FIR-ESR methods to enhance the effectiveness of motional and structural studies. New, more detailed models of the complex molecular dynamics of biomolecules will be incorporated into the analysis of the ESR experiments.